Papillary carcinoma of thyroid is associated with indolent biologic behavior, low incidence of distant metastases and good prognosis. Certain special variants, however, such as the TCV, insular and columnar types, have been associated with poor prognosis, early metastases and death. We will study this unusual forms of cancer to evaluate the presence or absence of enzymes that play an important role in tumor invasion and metastases and compare them with normal thyroid tissues. Our aim is to demonstrate the possibility to use these enzymes as tumor markers.